Boeing Co. is bracing for the first strike in nearly three decades at its St. Louis-area defense factories after union members rejected the company’s modified contract offer.

More than 3,200 Boeing employees at defense division factories in the St. Louis area could walk off the job Sunday, halting production of the aerospace company’s fighter jets.

Boeing ( NYSE: BA) is facing the prospect of its first strike in nearly 30 years at its defense manufacturing facilities near St. Louis, after union members rejected a revised labor agreement.